Tom Harris was born on 20 February 1964, the third son of Tom, a lorry driver, and Rita, an office clerk. He spent the first 20 years of his life in Beith, Ayrshire.

He originally attended Spiers School, but became a pupil at Beith Primary in 1972 after comprehensive education forced the closure of Spiers. In 1976 he began his secondary education at Garnock Academy.

On leaving, in 1982, he was unemployed for a year before starting a mechanical engineering course at Glasgow College (now Caledonian University). Engineering, he quickly discovered, was not for him, so he applied for a new two-year course in journalism at the then Napier College (now University) in Edinburgh.

It was at this point, in 1984, that Tom joined the Labour Party. He first started attending meetings in his local constituency, Edinburgh South, while a student at Napier. After he left college in 1986, he joined the staff of the East Kilbride News as a trainee reporter and moved to Cathcart constituency in Glasgow. He quickly became involved in the local Labour Party, becoming branch secretary and delegate to Scottish Labour conference.

In 1988 Tom became a reporter on the Paisley Daily Express, one of only two local daily newspapers in Scotland. In the course of the next two years, Tom became further immersed in Labour politics. He was Cathcart's delegate to national conference in 1989 where he spoke out against those who were refusing to pay the poll tax. In the same year he led an investigation into the activities of the Militant tendency in Cathcart Labour Party, which culminated in the expulsion from the party of eight people (including Ronnie Stevenson, who subsequently stood against Tom at the 2001 and 2005 general elections).

In 1990 Tom was recruited by the Labour Party in Scotland as its first ever full-time press and publicity officer, where he oversaw the party's media strategy in three parliamentary by-elections (Paisley North and South in November 1990 and Kincardine & Deeside a year later), the 1992 general election and the district council elections the same year. During this hectic period, Tom had the privilege of working closely with Donald Dewar, John Smith, Gordon Brown, Robin Cook and various other shadow cabinet members, including the then Shadow Employment Secretary, Tony Blair.

Realising that working for a party of government would be a lot more interesting than working for a party of opposition, Tom looked forward to the April 1992 general election with high hopes. But then it all went horribly wrong. Facing yet another stint in opposition, with morale in the party so low that more and more members were even considering supporting electoral reform as the surest way of getting unpopular parties into government, Tom left the party's employment to work part-time for his own MP, John Maxton, while trying to build up a career as a freelance journalist.

In January 1993 Tom became a press officer with Strathclyde Regional Council, a post he held until local government reorganisation in April 1996, when he became the senior media officer for Glasgow City Council. Six months later he became public relations manager for East Ayrshire Council in Kilmarnock and in July 1998 was appointed as chief public relations and marketing officer with Strathclyde Passenger Transport Executive, or SPT.

By January 2000, when John Maxton announced that he intended to retire at the next general election, Tom had become chair of Cathcart Constituency Labour Party, and soon announced his intention to stand for the Labour nomination in Cathcart. Eight months later, Tom was selected as Labour's prospective parliamentary candidate for Cathcart.

In May 2001, when Tony Blair announced that polling in the general election would take place on 7 June, Tom resigned from SPT. On 7 June 2001, he became Labour MP for Cathcart with a majority of 10,814, a majority of 39.5 per cent over all other parties - slightly up on Labour's 1997 result.

He made his maiden speech in the House of Commons on 27 June 2001. It wasn't very good, but the important thing was to get it behind him. Tom became a member of the House of Commons Science and Technology Select Committee, instigating its investigations into the effect of light pollution on the work of amateur astronomers. He was active in various all-party (non-statutory) groups and in the Parliamentary Labour Party's Northern Ireland and Treasury committees. In 2003, in the crucial votes on Iraq, Tom voted to support the government's position. In July 2003, he was appointed as parliamentary private secretary (PPS) to John Spellar, Minister of State for Northern Ireland, a position he held until the 2005 general election.

Following a redrawing of the boundaries of Westminster constituencies, Tom was selected as Labour's candidate for the new Glasgow South seat, which includes all of the existing Cathcart constituency, plus about a third of the former Govan seat. At the 2005 general election, Tom was re-elected to Parliament with a majority of 10,832 over the LibDems. He was subsequently appointed as PPS to Patricia Hewitt MP, Secretary of State for Health.

In September 2006, Tom was appointed Parliamentary Under Secretary of State at the Department for Transport, with responsibility for rail, light rail and cycling. When Gordon Brown became prime minister in June 2007, Tom was re-appointed to transport with an expanded remit which included railways and the trunk road network.

He is a member of a number of other all-party groups whose subjects include Poverty, the BBC, ME, Rail, Astronomy & Space Environment, and Islam. He is also a member of Amicus, the Co-op Party, The Fabians and the Christian Socialist Movement. Tom has maintained a constituency office in the constituency since shortly after he was elected. During his first term, this was based at the Couper Institute in Cathcart. Following a fire there in February 2006, he moved his operation to the Queen's Park Football Club offices near Hampden Park.

Tom lives in the constituency with his wife and three sons. His personal interests include astronomy, science fiction, cinema and karaoke (no, seriously). He hillwalks when he can and has also taken up tennis recently, but he's not very good at it.